The invention relates to a process for heating a moving web, in particular a corrugated board web, as well as a preheater.
A preheater for a corrugated board web has been disclosed by DE 23 02 449. This known preheater has a heating drum that is driven to rotate. The web is supplied via a stationary inlet to the heating drum and is carried away from it via a stationary outlet. The heating drum is associated with a deflection roll for the web, which can be pivoted concentrically around the central axis of the heating drum. The pivot angle determines the contact area of the web on the heating drum and therefore the heat quantity to be transmitted. The pivoted deflection roll carries the web along and moves it over the heating drum, wherein the winding angle can be adjusted. This produces the heat transfer from the heating face of the drum into the adjoining outer layer of the web. In order to prevent the incoming web from touching the outgoing web, normally a second roll is provided in the circumference direction of the heating drum. For safety reasons, these rolls are spaced apart from the rotating heating drum by 120 mm. It is disadvantageous that the web can only wind around the heating drum with a maximal angle of approximately 270.degree.. Furthermore, the web can only be heated on one side by the heating drum, by means of which an uneven heating of the web takes place. There is also the danger that at high web speeds, due to the merely unilateral web heating, the adhesive applied in the adjoining adhesive mechanism does not set, i.e. develop a certain adhesive effect, rapidly enough.